DigaSystem IdentityServer is DAVID Systems implementation of an OpenID Connect Server.

IdentityServer supports DigaSystem credentials (read from the DigaSystem RIGHTS.PAR file) including credentials synced with Active Directory.

OpenID Connect allows authentication and authorization to 3rd party without having to share a password with them. 

What is OpenID Connect?

OpenID Connect is a simple identity layer on top of the OAuth 2.0 protocol. It allows Clients to verify the identity of the End-User based on the authentication performed by an Authorization Server, as well as to obtain basic profile information about the End-User in an interoperable and REST-like manner.

OpenID Connect allows clients of all types, including Web-based, mobile, and JavaScript clients, to request and receive information about authenticated sessions and end-users. 

(also see https://openid.net/connect/

What is OAuth?

OAuth is an open standard for access delegation, commonly used as a way for Internet users to grant websites or applications access to their information on other websites but without giving them the passwords. This mechanism is used by companies such as Amazon, Google, Facebook, Microsoft and Twitter to permit the users to share information about their accounts with third party applications or websites.